Bonds explained: what they are and why you might own them

Bonds are loans you make to governments or corporations in exchange for regular interest payments. They're less exciting than stocks — and that's exactly their job. Here's how they work and when they belong in a portfolio.

By StevenPG April 16, 2026 Reviewed May 21, 2025 6 min read

Educational content only — not financial, tax, or legal advice.

Most investing articles spend 90% of their words on stocks. Bonds — the other half of the classic “60/40 portfolio” — get treated as the boring older sibling. That’s a mistake. Bonds do something stocks can’t do reliably: provide stable income and act as ballast when equity markets fall. Understanding them isn’t optional once you’re actually building a portfolio.

What a bond actually is

When a government or corporation needs to borrow money, they can issue bonds instead of taking a bank loan. A bond is a formal IOU: you lend them money (the face value or principal), they pay you regular interest (the coupon) on a schedule, and at the end of a fixed term (the maturity date) they return your principal.

Example: you buy a 10-year US Treasury bond with a $1,000 face value and a 4% coupon. You’ll receive $40/year in interest payments, paid twice yearly at $20 each, for 10 years. At the end, you get your $1,000 back.

The bond market is larger than the stock market globally. Bonds are how governments finance deficits, how companies borrow for expansion, and how pension funds and insurance companies match long-term liabilities.

Types of bonds

By issuer:

US Treasuries: backed by the US government (technically “risk-free” in nominal terms). T-bills (< 1 year), T-notes (2–10 years), T-bonds (10–30 years). Interest exempt from state and local taxes.
Municipal bonds (“munis”): issued by states, cities, counties. Interest is usually exempt from federal income tax and often state taxes too — this makes them particularly valuable for high-income taxpayers.
Investment-grade corporate bonds: issued by financially solid corporations (credit ratings BBB/Baa and above). Pay more than Treasuries to compensate for slightly higher default risk.
High-yield (“junk”) bonds: issued by lower-rated companies. Higher coupon, meaningfully higher default risk. Behave more like equities during stress periods.

By inflation protection:

TIPS (Treasury Inflation-Protected Securities): the principal adjusts with CPI; coupon paid on adjusted principal. Protects purchasing power.
I-bonds: US savings bonds with a fixed rate plus a CPI adjustment component. Not tradeable; annual purchase limit $10,000 per SSN.

The price-yield relationship: the most confusing thing about bonds

When interest rates rise, existing bond prices fall. When rates fall, existing bond prices rise. This inverse relationship trips up most first-time bond investors — and it matters.

Here’s why: if you hold a bond paying 3% and new bonds are being issued at 5%, your 3% bond is less attractive. Its market price will fall until its effective yield (coupon ÷ current price) equals the new market rate of 5%. This price drop is the market’s way of making existing bonds competitive with new ones.

This is why 2022 was such a brutal year for bond funds: the Fed raised rates from near-zero to 5%+ in under a year, causing bond prices to drop sharply. Investors who held bonds to maturity still received their full principal — the loss only realized if they sold early.

The duration of a bond measures its sensitivity to interest rate changes. Long-duration bonds (20–30 year Treasuries) swing dramatically with rate moves; short-duration bonds (2-year notes) barely twitch. This is why many conservative investors hold shorter-duration bonds.

What bonds do in a portfolio

The standard argument for holding bonds in a diversified portfolio:

Stability and income. Bonds provide predictable cash flows — the regular coupon payments — regardless of stock market conditions. During retirement, this is often the “salary” your portfolio pays you.
Diversification. In most recessions and market panics, investors flee to the safety of government bonds, driving bond prices up even as stocks fall. The classic “flight to quality.” This means bonds have historically had a low or negative correlation with stocks during the worst equity drawdowns.
Rebalancing fuel. When stocks fall sharply, your bond allocation (now a larger percentage of the portfolio) can be sold to buy equities at lower prices — systematic “buy low.”

The 2022 exception is worth noting: both stocks and bonds fell simultaneously because the driver (rapid Fed rate hikes) was bad for both asset classes. The stock-bond correlation can turn positive in inflationary environments, reducing the diversification benefit.

How much to hold: the age-in-bonds rule and beyond

The old rule of thumb was to hold your age as a bond percentage (60 years old → 60% bonds). Modern versions of this advice tend to use a more aggressive starting allocation and shift more gradually:

In your 20s and 30s: 0–10% bonds is reasonable if you have a long horizon, high risk tolerance, and stable income.
40s–50s: 10–30% as you approach the distribution phase and sequence-of-returns risk becomes a real concern.
60s and in retirement: 30–50%+ depending on Social Security income, spending flexibility, and time horizon.

The safe withdrawal calculator lets you test how different stock/bond allocations affect portfolio survival over 30 years.

Bond funds vs. individual bonds

Most individual investors hold bonds through bond funds (ETFs or mutual funds) rather than buying individual bonds, for several reasons:

Diversification: a single bond fund holds hundreds or thousands of bonds, eliminating single-issuer default risk.
Liquidity: bond funds trade like stocks; individual bonds (especially corporate bonds) can have wide bid/ask spreads.
Automatic reinvestment: coupons are reinvested automatically in the fund.

The tradeoff: unlike holding an individual bond to maturity, a bond fund never “matures” — it’s a rolling portfolio of bonds. You’re always exposed to interest-rate risk. This matters if you’re planning to spend a specific sum at a specific time.

Try it yourself

The safe withdrawal calculator lets you test how a stock/bond mix performs under different return assumptions over a 30-year retirement. The retirement calculator helps project the accumulation side using your current savings and contribution rate.